Tandem valve concrete pump



Nov. 24, 1936. c. F. BALL TANDEM VALVE CONCRETE PUMP 2' Sheets-Sheet 1 Filed Oct. 12, 1935 2 2 a w a w a g w u. i a a .l, l a i 3 m .2 3 a 7 Charles zw' zz,

c. F. BALL TANDEM VALVE CO NCRETE PUMP '2 Sheets-Sheet 2 Filed Oct. 12. 1935 v Charles EB all,

AWWWMH I Patented Nov. 24, 1936 TANDEM VALVE CONCRETE PUMZB Charles F. Ball, Wauwatosa, Wia, assignor to,

Chain Belt Company, poration of Wisconsin Milwaukee, Wis., a cor- Application October 12, 1935, Serial'No. -14,793

16 calms. (01. 103-227) My invention relates to concrete pumps, for

pumping plastic concrete mixtures through an associated pipe-line from the pumps convenient station on the job into the erection-forms in 5. which the mixture will be compacted and allowed to set or harden.

Pumps for this purpose, of substantially the specific construction shown in Patent No. 2,017,- 975, granted October 22, 1935, to Jacobus C. Kooyman, (on his application co-pending herewith, Serial No. 652,077, filed January 16, 1933) have been in extensive commercial use for several years past; and in one of its aspects my invention directly improves on such Kooyman pump, for I desirably use in the embodiment of my invention various features set forth in said patent, as will hereinafter more fully appear.

Field experience has shown that for many im- I portant concrete structures the mixture best suited to the job, to' give desired strength and quality to the finished work'and as well to minimize cost of the concrete, is'of the sort commonly referred to as a. small slump mixture containing a high percentage'of graded coarse aggregates. Also, such mixtures,-being relatively very dry, dense and diflicultly workable at best-generally have been extremely hard to handle by pump and pipe-line with entire satisfaction, prior to my invention.

, In a more general aspect, one important object of m'yinvention is to provide an improved I pump of the reciprocating-piston type so organized that it will handle a very wide range of concrete mixtures including the very diflicult ones last mentioned, and will handle-the latter with a reliability that avoids troubles and shutdowns. with an efficiency that insures steady delivery of a very high percentage of the pumps theoretical, delivery-capacity, and with an over-all econwill excel in each stated respect the performance characteristics of any previously existing or proposed concrete pump of which I am aware.

Other and further objects of my invention will become apparent hereinafter, and success in attainment of my objects has been fully demonstrated in the quite extensive commercial use to which my improved pump, substantially as shown in the drawings hereof, has already been put.

The commerciaily desirable sniall slump mixtures above referred to are commonly characterized as follows: The larger aggregates, of over .25 inch screening size, generally preponderate over the liner aggregates. The graded coarse aggregates are made up of a number oi different omy, due to savings of labor, time and waste, that screening sizes, in due proportions of each, with the coarsest pieces-sometimes being notably large in proportion to the cylinder-bore of the pump to be used-say of 3 inch screening size, to be han- "dled by a pump of say 8 inch bore and 12 inch stroke and a pipe line of the same or slightly lessinternal diameter. Thefine aggregates as well are also preferably graded, from nearly .25 inch size to fine sand, and under the proper mixing these finer particles mingle so densely with the 'coarser pieces as to'leave an approximate minimumrof voids. For this reason, and because of the coarseness(of the largest pieces, the re-. quirement of cement-and-water paste requisite to coat all pieces and particlesof the aggregates 15 and to fill the voids is substantially minimized, with resultant economy in cement requirement;

.and with advantage in reduction of the heat of hydration consistent with such reduction in cement content; while the comparative smallness of the fluid content enhances early high strength of the placed concrete.

As affecting the somewhat obscure conditions of inter-action between difierent ingredients of the mixture, and between the mixture and the pump and its pipe-line, under the varying forces that act upon the mixture in the pumping operation, the inherent resistivity of such mixtures to successful, reliable pumping is unquestionably ag- 'gravated greatly may call the solid densitytthereof. The lubricating effect of the paste and the fines, as be tween pieces of the aggregates themselves and as between them and the internal surfaces oi. the

pump and pipe. line, islessened by the meagerness of moisture; the resultant small slump orv steep1angle of repose militates against passing of the mixturethrougli the mouth or open end of the cylinder to charge the cylinder under con-,

of lubrication, together with the heightenedpressure that must be exerted by the pump on its working stroke to propel a given line-pipeful of concrete, all enhance the tendencies of the 5 concrete to stow at restrictions" within the pumping system and to pack solidly and selfsustainingly in passages and vpassage-enlargements.

In accommodating these dimcult characterisby the dryness and what I 30 I tics of this class of concrete mixtures with the stated reliability, efliciency and economy, and as well in improving over prior pumps in general serviceability, I find the valving arrangement and particular constructions hereinafter described to give excellent results.

In the accompanying drawings, in which like reference characters designate like parts in all views:

Figure 1 is a side elevational view, partly diagrammatic, of a pump of the same general type as said Kooyman pump, modified to embody' the present invention; the inlet and outlet valves being shown in. the positions they occupy during the working stroke of thepiston;

Figure 2 is a longitudinal sectional view, partly in elevation and partly diagrammatic, and upon a somewhat larger scale, of the pump illustrated in Figure 1, with the parts in the same relative positions, in which the piston has substantially completed its working stroke; V

Figure 3 is an enlarged transverse sectional view through the inlet valve structure, taken approximately on the plane indicated byline 3-4 of Fig. 2, looking in the direction of the arrows;

Figure 4 is a fragmentary view; similar to Fig. 2, showing the valves in the positions they occupy during the suction stroke of the piston; and

Figure 5 is a detailed longitudinal sectional view of the valve connecting rod which connects the inlet valve to its actuating mechanism.

Referring to Figs. 1 and 2, a chassis 5 and ground-wheels 6 carry the pump and its power plant, for convenience in moving the equipment to 'the'desired station on the job.

In general, the pump cylinder I, piston 3 and power plant for the pump are preferably substantially the same as employed in the Kooyman pump of said patent; 9 representing the piston rod connected to crank I 0 which is driven by reducing gearing, including large gear l2 on said shaft, driving pinion II on main drive shaft l4, pulley IS on said shaft l4, and belt l6 from a smaller pulley TI on the crank shaft of an internal combustion engine or other source of power mounted within the housing la.

The open end or mouth of cylinder! communicates with a passage IQ, of a valve housing structure 20, which also provides an inlet passage 2! extending upward into connection-with the gravity supply-hopper 42, and an outlet passage 22, coaxial with the cylinder and passage l9, and communicating at its outer end with the line pipe (not shown), which, of course, leads to the location of the erection-forms to be served. In best practice the internal diameters of the inlet and outlet passages are the same as,-or slightly larger,

or only slightly less than the bore of the pump cylinder, and in like manner, the cross sectional area of the pipe line which conducts the mixture to the point of placement is not materially greater or less than that of thepump cylinder and passages. For example, with an 8 inch pump,

i. e., one having an approximate 8 inch cylinder and passage diameter, it is preferable to employ Y for heavy duty, long distance, difficult-material jobs, a so-called 8 inch pipe, having an inside diameter of about 7.625 inches. In some instances, as where the material is to be pumped only a relatively short distance, a nominal 7 inch pipe, having an inside diameter of about 6.625 inches, may be used with an 8 inch pump but where any change of the substantially-uniform diameter relationship is made, the tapering of the diameter-reducing part is very gradual.

of the crank-shaft ll,

sageway 24 and 32, of a size not less than suffi cient to fully open the passage it controls when the valve is moved to'open position; in providing clearance with respect to its housing in the ported zone of the latter, suitable for circulation of the paste-flowable constituents of the mixture; and in being settable to move, in its passage-closing direction, to adequately restrict the passage it controls. The outlet valve is herein shown as substantially identical with the Kooyman construction; plug 3| having a cylindrical passageway 32 through it which is of the same diameter as .theoutlet passageway 22, so that in open position the valve passageway'32 aligns with and forms a smooth continuation of said outlet passage. In the "cut-011' position I the passageway 32 is angularly disposed, as in Figure 4, with the segments 33 at least partially closing of! the passage 22.

According to my invention the inlet valve 23 is constructed differently from, and is novelly ar-v ranged with respect to, said outlet valve; so that when the valve 23 is. in its closed or inlet-restricting cut-01f position at least a portion of its non-cylindrical passageway 24 is in tandem with the outlet passage 22 and its then-open valve 3|, thus to haveat least a portion of the concrete that is propelled by the, working stroke of the piston 8 sweep through the inlet valves said passageway; as would happen under-the conditions shown in Figures 1 and 2, were the system loaded, since the piston 8 is thereshown as nearing completion of its working stroke, with the inlet valve 22 in cut-oil! position and the outlet valve 30 fully open. Upon reversal of positions of both valves, as shown in Fig. 4,-i. e., during the suction stroke of the piston 8,the

,cut-off positioning of outlet valve 30 effectuthat the inlet valve shall be located substantially as close to the open. mouth of the pump cylinder as size requirements of its plug and other mechanical conditions will permit; also that its actuation from cut-oi! position to open position with respect to the inlet passageway 2| shall act to liven up the concrete in and adjacent to its own passageway 24 and shall have a tendency to push concrete into the mouth of the cylinder at commencement of the suction stroke, thereby permitting the concrete mixture in supply hopper 42 to slump into the inlet passageway, quickly establishing uninterrupted movement of the concrete from the hopper to the cylinder; and also that the transverse axis tionings of the valve, to, be described later.

Each of these desiderata has advantage in itself, and they interact advantageously, and also inconjunction with the outlet valve operation, in attaining the desired and stated results; of satisfactory operationsespecially on the stated difficult mixtures.

In the specific construction here shown, the

parti-cylindrical enlargement 25' of housing 2|,

in which said inlet-valve plug 23 works,- is ocated very close to the joint of the housing th the cylinder casing l of the pump; its transverse axis is located well above the horizontal'axis common to the pump cylinder and outlet passage, preferably at a height to bring the bottom are of the inlet-valve plug substantially in allgn- U ment with the pump-cylinder axis. The vertical axis of the inlet passage, is oifset rearwardly, toward the pump cylinder, as compared with; the transverse axis of the inlet valve.

Further, in the preferred specific construction of said inlet valve 23, the passageway through -it is of a width (as shown in Fig. 3) corconcrete and produce a pushing thereof back- 60 responding to the diameter of the inlet or outlet passagesbut is cut through a major lower part of the perimeter of the plug, leaving..,the end disc of the valve united by arather shallow segment 25, the peripheral extent of which is somewhat greater than that of the inlet passage 2|; and the bluntly-diverging inner walls of which substantially correspond, in sectional curvature, lengthwise of the plug, with that of the inlet passage.

It will be observed that when the valve seg-. ment 2,5 is in cut-off position, it will restrict the inlet passage to any adjusted extent for which its actuating mechanism may be set, which, with some e'asilypumpable mixtures, may be an ad- .justment for full closure of the inlet'passage.

and with more difiicult mixtures may be an adjustment for only enough restriction to assure stowing of the concrete within its ported zone adequately to complete the virtual closure of said passage; and that in its movementth'ence toward passage-openihg position, the descendingforward wall of thesegment will sweep the concrete below it downwardly and rearwardly toward the mouth of the pump cylinder; This movement tends to loosen and "liven-up" the aifected wardly toward thecylinder mouth. With the valve located above and adjacent the axis of the cylinder, this sweep of the valve has effect quite deep in the mixture belowit, and movement of the directly aflected-concrete doubtless aids materially in clearing the rear part of the valve passageway very eifectually ,-the resultant inflow of concrete from the hopper under gravity head and suction created by the piston movement being notably prompt and ample.

It will also be noted tliatbyoflsetting the inlet passage 2| with res'pectfi the valve axis, the effective distance from the valve to the mouth ofv the cylinder is lessened, team in the desiredv action, and at the same time the arcuate lengthof the upper, forward portion of the valve housing is increased so-asto substantially-coincide with the sweep of the valve segment25, for the avoidance of protruding it materially into said passage and for benefits in easing the valv'e'" op eration. 1 v a Concerning the effectual handling of the dry", dense mixtures in question, the arched pocket above the the outlet-passage, which is presighted by the passageway of the inlet valve when the latter is turned to cut-off position, is an. additional safeguard against'the clogging of the'inlet passageway; for although experience has shown that densely-packable goncrete. tends exasperatingly to pack self-sustainingly' within any poc ket in the pumping system under the high pressures necessary topropel the concrete to distant delivery points, the large-mouthed, arched shap-' of the inlet passage with the ,outlet passage, the

level at which the supply hopper 42 may be mounted is kept advantageously low. to facilitate loading, decrease head-room requirement,

etc.

'valv'ing action will also be the same; in that, since plug 3| has a central cylindrical passageway 32 through it of the same diameter as outlet passageway 22, the sidewalls thereof will encompass a cylinder-like section of concrete which in the closing action of the valve, is quickly and, in a sense, bodily displaced from the rest of the column contained in the passageway leading from the pump cylinder to the valve or from the valve to the pipe line, as the case may be, and in the. valves opening action is quickly replaced bodilyv into the concrete column. Onlya double shearing action of the concrete column'by the segments 33, and such friction as may be encountered in the turning of the valve plug, are involved in such revolving action and only a minimum power expenditure is necessary. On

ing to admit concrete from the feed hopper, that so 7 Since the outlet valve of my pump is identical with the Kooyman outlet valve construction, its

is responsible for the livening-up" of the concrete in the valve passageway and forcing; the same toward the cylinder mouth, and such action oi? the segrfient 25 when the valve is moving to open position, necessitates a greater expenditure .of power than that required for moving the outlet valve, especially when pumping "dry dense conerete, and more particularly after a long stoppage of the pump.

The valves 23 and 30 may be actuated by means of valve arms and 55 respectively, which arms in 'turn' are connected; by means of pitm'an or connecting rods 31 and 58, with oscillating levers 35 and, which levers are'moved by suitable cams on thecrank shaft .H, all in precisely the same manner as described in'the said Kooyman patent.

To secure best emcien'cy, it is common practice in concrete pumps of the Kooyman type, to have. the valve actuationtake place somewhat in ad vance of the piston movement. For example, before the end of the pressure stroke, the outlet valve starts to close and when the piston reaches the end of its stroke, the valve has been closed a substantial amount. The inlet valve will start to open very shortly after the movement of the outlet valve to closing position is started; but its initial movement is well in advance of the piston reaching stroke end. In pumping densely packable concrete mixtures, this advance movement of the inlet valve while the concrete is still'subject to high pump pressure, involves a further increase of power to eifect he valve plug movement. At times there ar extreme cases where the concrete is not of a uniform mixture, or a segregated mass of coarse aggregate concrete pieces enters the pump chamber, with the effect that the power required to actuate the inlet valve may be sumcient to actually stop the pumps opeihtion.

To insure reliably continuous operation in spite of the above recited difficult conditions, I have found it advantageous to novelly combine the inlet valve with a special type of valve connecting rod for actuating it, the rod being so constructed and arranged as to provide an overload relief in either direction of valve movement. This pressure relief is secured by means of pre-loaded springs; that is to say, springs which will not yield in the course of valve-actuation unless the force required to move the valve plug is greater than the predetermined spring loading. When moving the inlet valve in closing direction, the relief-spring action is usually brought into' play only in case the valve segment pinches a piece of aggregate between its edge and the inlet port so squarely that the piece will not squeezeout of its way, notwithstanding that conditions are quite favorable to the escape of pieces of aggregate from such a pinching action. In a pump of the size herein suggested, I have found that the spring giving relief to this closing action of the valve may be desirably pre-loaded to about 1700 pounds, with capacity for pressure-increase to about 4800 pounds. In the valve opening movement, the spring relief becomes effective whenever the power required to push the valve sector 25 to Fig. 4 position, against the resistance of the concrete below it, is excessive. this relief has suflicient yield-range to permit the valve plug, on occasion, to remain stationary until the pump piston has reached the end of its propulsion stroke, at which time the valve connecting rod is'well started on its valve-opening travel; and in existing pumps I have found good results to flow from the use of a spring pre-loaded to about 1800 pounds pressure, with a capacity for pressure increase to about 2900 pounds before the spring reaches solid length"which condition it reaches quite early in the valve-opening travel of the valve connecting rod, if the valve is offering suflicient resistance. It will be understood that at v the time the piston reaches the end of its propul-' sion stroke and ceases to apply pressure to the concrete that lies below the inlet valve, the out-' let valve 33 has partly closed, thereby reducing back-pressure on said concrete that underlies the inlet valve, and under these conditions the action of thecompressed relief spring is usually. suificient-if the inlet valve has remained this long in cut-oi! position-to start the inlet valve plug in rapid movement, so' that the latter catches up" i to its fully-open position at the same point in the Distons suction stroke as itwculd if positively,

actuated without spring relief. Should the re- The spring used in affording sistance to the opening movement of the inlet valve be excessivelyhigh, the valve connecting rod will actuate it positively to overcome such resistance, after the relief spring is compressed to solid length.

One form of my novel connecting rod for use in the stated combination with the inlet valve, which is shown in detail in Figure 5, has incorporated therein a coiled spring 45 which may be compressed when the valve rod is lengthened in the course of moving the valve to cut-oif position, a coiled spring 46 which is compressed whenever the valve rod is shortened in opening the valve; each of said springsbeing appropriately preloaded, as above indicated. The pro-loading compression of spring 45 can be changed by turning the adjusting nut 41.

- Whenever unusual resistance is encountered in the closing of the inlet valve 23, spring 45 is further compressed by outward movement of rod 50; the load being applied to the spring through rod head 48 and washer 49; and whenever unusual resistance is encountered in the opening of the valve, spring 46 is compressed by inward movement of rod 50; the load being applied to the spring through rod head 48, pressing against head SI of spring retainer 52.

Normally washer 49 is seated against the end of the shouldered'lining member 53 of the spring 45 and head 5| is seated against the interior shoulder of the'lining member 53 by spring 46. My con- :truction of the valve-connecting rod is such that each loaded spring, 45 or 46, is further'compressed independently of the other.

In rsum, I have found that troubles in feeding the pump 'by gravity and suction, and other obscure diiiiculties in reliably maintaining adequate output of the pump, are greatly lessened and the general performance of the pump is pumpable mixtures under adverse conditions (such as-frequent stoppage of the pump for a substantial time because of conditions which may be met in the placement of the concrete into the forms) by a suitable inlet valve positioned in appropriate relation to the juncture of the pump inlet and outlet pes, close to the point where said passages Jointly open to the mouth of the pump-cylinder,-and arranging the inlet valve to cooperate with a suitable outlet valve located be-- yond said juncture, so that during the working stroke of the pump a part, at least, of the outgoing mixture is propelled through the passageway of the "closed" inlet .valve before reaching the open outlet valve, which for this purpose is arranged in tandem'with the inlet valve. 1 By operating the rocking inlet valve, and a suitable outlet valve,

each for quick change of position and in suitable relation to the time-cycle of the piston-travel, said suitable outlet valve (of which the particular construction shown is a veryemcacious one) which serves to block return of concrete from the pipe --line to the cylinder on the suction strokeof the piston, also assures that the inlet vaiveis relieved of back-slip there-through of concrete seeking to return from beyond said inlet valve under the back-pressure of the concrete in the line-pipe (which Dressure may be-very considerable, particularly when the concrete mixture is being' pumped to an elevation scores offeet above thepumping station) ,and the eii'ectivet operation of the inlet valve-herein shown (to which various features of its construction and arrangement conjacent cylinder-mouthunder gravity and suction conditions; notwithstanding that, as compared with a similar pump having its inlet valve wholly above the juncture of the inlet passage with the outlet passage, the theoretical gravity head'of the mixture has been lessened, by a lowering of the supply hopper nearer to the axis of the pump-cylinder. And I have found that the advantages of the tandem valve arrangement are augmented by the employment of an oscillatingplug type of inlet valve of su tantially minimum practical diameter,'which i an inverted U-section in side view and which has its axis-of .oscillation located about half the plugs diameter above the axis of the outlet passage, and which further has its cut-oil segment coacting with an inlet passage that is offset on the valve housing in a direction toward the pump mouth; each of these factors, and as well the arched, wide-bottomed shaping of the pocket which the inlet valve presents toward the outlet passage during the working stroke of the piston, contributing to the eihcacy of the pumping operation and to the mechanical simplicity, low cost, and durability of the machine itself. Also, the use of my safety doubleacting valve-connecting rod aids in assuring continuous operation of my concrete pump on long runs without stoppage for repairs or replacement of damaged parts.

I claim: 7

1. In a pump for plastic concrete mixtures, having a working chamber, a pressure member'working therein, and inlet and outlet passages communicating therewith, the combination of inlet and outlet valves controlling said inlet and outletpassages respectively, said valves being arranged in tandem with respect to said chamber and outlet passage, whereby the mixture moved along the outlet passage on the working stroke of said pressure member passes through both said valves.

2. In a pump for plastic concrete mixtures, hav ing a working chamber, a pressure member working therein, and inlet and outlet passages .com-

' municating therewith at a common point, the

combination of an inlet valve positioned at the junction of said passages in close proximity to said chamber, arranged to control the flow of the mixture from the inlet passage to the chamber; and an outlet valve in said outlet passage beyond I said inlet valve, said valves 'being so .arranged that the mixture moved along the outlet passage on the working stroke .of said pressure member passes through both of them.

. 3. In a pump for plastic concrete mixtures, hav-.

ing a working chamber, a pressure member working therein, and inlet and outlet passages communicating therewith and with each other, an inlet valve positionedat the juncture of said passages, arranged to control the how of the mixture from the inlet passage to the chamber, said valve having a mixture flow passage affording constant.

communication between said working chamber and outlet passage, and being subject to back-slip of the mixture'therethrough when not in cut-off position; and an outlet valve in said outlet passage beyond said juncture, arranged to prevent back-slip through said inlet valve.

4. In a pump for plastic concrete mixtures, having a working chamber, a pressure member working therein, and inlet and outlet passages communicating therewith and with each other, an inlet valve positioned at the juncture oi said'passages for controlling the flow 01' mixture from the inlet passage to said chamber, said valve being arranged to afford in both its open and closed positions communication therethrough between said chamber and outlet passage, a feed hopper surmounting said valve close to the low level of the top of the valve, and an outlet valve in said outlet passage, arranged to prevent back-slip of the 4 mixture through said inlet valve.

5. In a pump for plastic concrete mixtures, having a working chamber, a pressure member working therein, and inlet and outlet passages communicating therewith and communicating with each other close to themouth 01' said chamber, an oscillatory inlet valve positioned to extend into the juncture of said passages, having a segment which in one position at least partially restricts said inlet passage to control the flow of mixture to said chamber, said valve having a passageway which in either position of the segment atiords communication between said chamber and said outlet passage and in the open position 01.

said valve affords communication between said chamber and the inlet passage; and an outlet valve in the outlet passage movable-between respective positions in one of which it opens the outlet passage and in the other of which it re-'- stricts said passage at least sufilciently to produce stowing of. the mixture and prevent backslip thereof through said inlet valve.

6. A concrete pump eilective to handle small slump concrete; mixtures of graded coarse aggregate, having a cylinder open at one end; a piston working therein; inlet and outlet passages communicating in common with the open mouth of said cylinder and with each other close to'said mouth; a U-section oscillatory inlet valve posi-- gregate, having a cylinder open at one end; a" piston working therein; inlet and outlet passages communicating in common with the open mouth of said cylinder and with each other .close to said mouth; a U-section oscillatory inlet valve'positioned at the juncture of said passages, having a valving-segment coacting with the inlet passage to control the flow of mixture from said passage to said cylinder mouth and having part of its own passageway coinciding with the outlet passage in either position of saidvalve, said valvingsegment being arranged to urge the .concrete mixture adjacent thereto toward the open end of said cylinder during the opening movement of the valve; and an outlet valve controlling the opening and closing of the outlet passage beyond said juncture.

8. A concrete pump effective to handle small slump concrete mixtures embodying graded coarse aggregates, having acylinder-open at its end; a

piston working therein; inletand outlet passages communicating in common with the open end of said cylindenand with each other close to said end; a U-section oscillatory inlet valve positioned at .the juncture ofsaid having a valving-segment arranged to control the flow of mixture ironrsaid inlet passage to-said open cylinder end, and having part otits own passageway coinciding with the outlet passage in either position oi said valve, the oscillatory axis 01' said valve being transverse to and above the axis of said outlet passage; and an outlet valve controlling said outlet passage beyond said juncture.

9. A concrete pump eflective to handle small slump concrete mixtures embodying graded coarse aggregates, having a cylinder open at its end; a piston working therein; inlet and outlet passages communicating in common with the open end of said cylinder, and with each other adjacent said end; a U-section oscillatory inlet valve positioned at the juncture oi said passages, having a valvingsegment arranged to control the flow of mixture from said inlet passage to said open cylinder end, and having part of its own eway coinciding with the outlet passage in either position of said valve; the axis oi said inlet passage being oflset toward said open cylinder end, relative to the axis of oscillation 01' said inlet valve; and an outlet valve controlling said outlet passage beyond said juncture.

"10. A concrete pump eflective to handle small slump concrete mixtures embodying graded coarse aggregates, having a cylinder open at its end; a piston working therein; inlet and outlet passages communicating in common with the open end or said cylinder, and with each other adjacent said end; a U-section oscillatory inlet valve positioned at the junctureof said es, having a valving-segment arranged to control the flow of mixture from said inlet passage to I said open cylinder end, and having part of its passages 01' substantially equal mixture from said-inlet m:-

own passageway coinciding with the outlet passage in either pomtion of said valve, the axis 01' oscillation of said valve being transverse to and above the axis of said outlet e, and the axis of said inlet passage being oil'set relative to said valve-oscillation axis toward said open cylinder end. said valving-segment being movable i'rom ,inlet-passage-restricting position to open position without substantially entering said outlet and an outlet valve controlling said outlet H s; e beyond said juncture. 11. A concrete pump effective .to handle small slump concrete mixtures em odying graded coarse aggregates, having a cylinder open at its end; a piston working therein; inlet and outlet com-- municating in common with the open end 01 said cylinder, andwith each other adjacent said end; a U-section oscillatory inlet valve positioned at the juncture of said es, having a valving-segment arranged to control the flow at to said open cylinder end, and having part 0! its own passageway coinciding with the outlet e in either position oi. said valve, the width oi said valve eway being substantially equal to the diameters 01' said inletand outlet 1 whereby there is provided a wide-mouthed arched chamber beneath said valving segment when the valve is in closing position; an'oscil-u latory outlet valve' controlling said outlet passage beyond said juncture, arranged to at least partially restrict said outlet e when in closing position. and to provide a smooth continuation of, said passage when in open position: said inlet and outlet valves-being of approximately the same diameter; and a low height teed hopper sin-mounting said inlet valve.

- 12. In a pump for plastic concrete mixtin'es, a working chamber; a pressure member working in said chambeminlet and outlet com- -municating with said-chamber and th each the valve segment aflords communication between the valve segment aiIords communication between said chamber and said outlet a: and in the open position of the segment also aiiords communication between said chamber and the inlet passage; means including an overload release device for moving said valve from one position to the other,'said device being arranged to function diirerentially during movements of the valve to and from inlet "closing" position; and a valve controlling said outlet e.

13. In a pump for plastic concrete mixtures, a working chamber; a pressure member working Y in said chamber; inlet and outlet a communicating with said chamber and with eachother; an oscillatory inlet the juncture oi said 1 having a segment which in-one position at least partially restricts said inlet u: e tocontrol the flow oi mixture to said chamber, said valve having'a valve positioned at 20 6W3! which ineither the open or cloud position of I the valve segment affords communiuttion between said chamber and said outlet and in the open position ot the segment also aiiords communication between said chamber and the inlet means including an overload release device for moving said valve from one position to the other, said device having a plurality oi resilient elements, pro-loaded to different degrees and arranged to function diilferenflally during movements of the valve to and from inlet "closing" position; and a valve controlling. said 14. Inappiorplssticconcrete'mixturma said chamber; inlet and outlet es communicating with said and with each other; an oscillatory inlet valve positioned at the juncture of saidhaving a t which one position at least partially-restricts saidinletpassagetocontroltheflowotmixtureto said chamber, said valve having a eway which in either the open or "closed" position of said chamber and said outlet e, and in the openposition or the segment also aflords communication between said chamber and the inlet e; means including an overload release device for moving said valve iromone position to the other, said device having a pinrality of resilient elements pro-loaded to diii'erent degrees and arranged to iimction diiiereng tially during movements or the valve to and rrom inlet "closing position, the element which functions during movement to closing position being pre-loaded less than the element which functions during movement to open position and a valve controlling said outlet e.

15. In a pump for working chamber; a pressure member working in said chamber; inlet and outlet communieating with said chamber and with each other; an oscillatory inlet vain positioned at the juncture 01' said es, havinga segment which in one position at least partially restricts said inlet eto control the .ber,saidva'lve havingapassagewaywhich: either the open or closed". position of the segment affords communication between said, chamberand said outlet pasage, and in the openpositionotthesegmentalsoaii'ordscom 'u plasticconcretemixturma s flowotmixtureto sn'idlo munication between said chamber and the inlet passage; means including an overload release device for moving said valve from one position to the other, said device having a plurality of resilient elements pre-loaded to different degrees and arranged to function differentially during movements or the valve to and from inlet "closing position, the element which functions during movement to "closing" position being pre-loaded less and having greater pressure-rincrease capacity than the element which functions during movement to open position; and a valve controlling said outlet passage.

16. In a pump for plastic "concrete mixtures, a

working chamber; a pre'ssure member working therein; inlet and outlet passages communicating juncture.

with said chamber and with each other; an inlet valve positioned at the juncture of said passages,

having an oscillatory plug, U-shaped in axial section, providing a valving segment arranged to coactwith the inlet passage to control the flow or mixture therefrom to said chamber, and a passageway adapted to aflord communication with said outlet passage in either the open or closed? position or the segment,- said segment being or flattened V-shape in transverse section and arranged to urge the concrete mixture adjacent thereto toward said working chamber during the opening movement of the valve; and a second valve, controlling said outlet passage beyond said CHARLES F. BALL. 

